The current automatic fire extinguishing methods often use electric pumps with high power equipped with pressure relays connected to fire alarm sprinkler. In case of fire, the file alarm sprinkler is broken, thus reducing the pressure in the permanent system, and activate the relay which starts the pump to supply water to the fire extinguishing system. When the power is cut off, the pump operated by the reserved generator will function. To remedy the leak due to defective assemble, a third pump will a pressure relay connected with the system will automatic start to supply water continuously.
Advantages:
The automatic fire extinguishing system can quickly put out the fire if it is regularly maintained according to the technological requirements.
Disadvantages:
1. Depending on the Power Supply:
                The inevitable disadvantage of the technological solution is that the system is completely dependent on the power supply: if the power is disconnected and the generator breaks down, then the whole system is completely dead. Therefore, although there is no fire, the system must be regularly operated to check the reliability, which causes environmental pollution and constantly consumes electricity and petrol. Meanwhile, the fire extinguishing system itself cannot produce benefit to recover the invested capital.        If the water tank is used to supply water automatically, pumps must be used to provide water, and the cost of building the water tank is very high.2. Occupancy of Large Land Area:        Being operated by high power, the fire extinguishing itself becomes a possible cause of fire; therefore it must be constructed a long way from the area to be protected, which takes up some land, and in case of fire, the system cannot protect itself.3. High Consumption of Water:        When the system operates to put out a fire, the water loss due to the effect of the fire is little, but the amount of water for cooling the nearby things runs to the gutter is much greater. Whereas, at the constructions where there is high possibility of fire and explosion, the safety regulations for fire prevention and protection require a great source of water for fire extinguishing, which is often beyond the supply capacity; therefore, it is necessary to build an additional pipe to suck water from natural sources, such as ponds, lakes, rivers, and streams, and even sea water to put out the fire. The quality of this supplementary source of water is often low, and it easily produces rust and blocks the fire extinguishing system and is likely to become exhausted in summer.4. Reducing the Fire Extinguishing Capacity of Water and of the Automatic Fire Extinguishing System        The cheapest and best fire extinguishing agent is water, but it is not used for putting out fires caused by petrol and oil, which is highly flammable because when water is added, petrol and oil will float on the water surface and will likely to spread the fire. However, if chemicals are mixed with water for extinguishing, after the fire being put out, it is this mixture that deteriorates petrol and oil.        Each fire extinguishing pumping system has three pumps but they can supply only one fire extinguishing agent while the site often consists of different objects with various chemical and physical properties. Therefore, in many cases, after putting out the fire, the objects are also damaged by the fire extinguishing agent (i.e.: water destroys documents, electronic and electrical equipment, chemicals, food or when in contact with alkaline metals, calcium carbide, the fire will become even more violent, . . . )        When the temperature is lower than O C, the water is iced, so the whole fire extinguishing system is halted.5. Limiting the Promptness        Due to the use of pumps, there is negative pressure in the sucking pipeline, which will make it difficult to be air-tightened. Even when the pumps are in good working condition, the fire extinguishing is still slow because they cannot suck water instantly.6. The System has to be Imported at High Cost        The system has three pumps with many automatic control cabinets which are interconnected, sophisticated, and sensitive. The higher power, it has the higher it costs (up to hundreds of thousands of US$); therefore, a quite large number of units, which are likely to suffer high fire risk, cannot afford to equip with the automatic fire extinguishing system.        